The present invention relates to mounts for suspension actuators and dampers and more particularly, to top mounts for a hydro-pneumatic struts.
A typical top mount secures the upper end of a suspension actuator or damper to a body. Conventional top mounts include at least one resilient element (rubber cushion), to isolate and reduce the transmission of input forces to the body. A top mount is generally required to be firm enough to support the weight of the body while simultaneously resilient enough for isolation purposes. For certain inputs deflection of the top mount is desirable while for other inputs it is preferable for the top mount to resist deflection.
Single path top mounts are known, wherein the actuator or damper rod and a coil spring seat are fastened together and the load path is through a single rubber cushion. The single rubber cushion accommodates the forces generated by both the actuator or damper and the cooperating coil spring. The rubber cushion is preloaded by the vehicle's weight and therefore, compression set of the rubber cushion becomes a concern. It is also known that such single path mounts may exhibit inadequate tunability features.
Dual path mounts are known, wherein the actuator or damper rod and the coil spring seat are not fastened together and wherein the load path is through separate rubber cushion assemblies. A first rubber cushion assembly engages the coil spring and supports the vehicle's weight and the second rubber cushion assembly engages the actuator or damper rod and is not preloaded by vehicle weight. These dual path mounts exhibit somewhat improved tunability over conventional single path mounts but may provide a compromised spring rate to accommodate the two different forces.
With the described single and dual path mounts, the coil spring supports the weight of the vehicle and creates a force that is proportional to the relative velocity between the vehicle's wheel and its body. The coil spring and actuator or damper are attached between the wheel and the body by the top mount. Therefore, the top mount must support the total weight of the vehicle and provide acceptable isolation.
Hydro-pneumatic struts are known which function as both a spring and a damper. Because there is no conventional coil spring component in a suspension incorporating hydro-pneumatic struts, the conventional dual path mount described above cannot effectively be used with a hydro-pneumatic strut. A conventional single path mount can be utilized with a hydro-pneumatic strut but due to large vehicle corner weight in the vertical direction, the conventional mount generally exceeds the current vertical space available in the strut tower area for many vehicles. Therefore, an acceptable top strut mount that fits within the available limited space of a vehicle and provides desirable performance characteristics is required.